1. Field of Invention
The present invention relates to a touch sensing device and method thereof. More particularly, the present invention relates to a touch sensing is device and method capable of sensing touched position(s) from various types of touch-input objects, such as fingers and styli.
2. Description of Related Art
Recently, various types of touch-sensing techniques, such as resistive touch sensors, capacitive touch sensors, surface acoustic wave touch sensor and infrared touch sensors, are popular and well developed in many applications.
The resistive touch-sensing technique determines a touched position by measuring a voltage (or potential) corresponding to the touched position. The voltage, corresponding to the touched position, can be measured when top and bottom conductive layers of the resistive sensor panel contact with each other at the touched position due to the touch pressure.
There are two common types of capacitive touch sensing techniques. One of them is the Surface Capacitive Touch (SCT) panel, and the other one is the Projective Capacitive Touch (PCT) panel.
The Surface Capacitive Touch panel detects the touched position based on the measurement of the resistance(s) between the touched position and the sensor electrode(s). The measured resistance is proportional to the distance between the touched position and the sensor electrode. Based on aforesaid proportional relationship, the touched position can be determined by calculating the resistance values seen from the sensor electrode(s).
The Projective Capacitive Touch technique requires multiple sensors placed beneath the cover glass to detect a touch input. Reference is made to FIG. 1, which is a schematic diagram illustrating a Projective Capacitive Touch is panel 100 in prior art. As shown in FIG. 1, the sensor of the Projective Capacitive Touch panel 100 has a conductive path pattern formed by a transparent conductive material, such as Indium Tin Oxide (ITO). The conductive path pattern is normally called the ITO pattern. The allocation of the conductive path pattern needs to be planned carefully. As shown in FIG. 1, the Projective Capacitive Touch panel 100 includes conductive traces 120 in direction X and conductive traces 140 in direction Y. The Projective Capacitive Touch technique measures the capacitance change due to the input device (such as the fingers) being close to the sensors. The capacitance change seen by a single sensor can determine whether or not a touch action happens at the location of the sensor. To determine the touched position, the capacitance changes seen by multiple sensors (or all sensors) are required. The touched position can be calculated on a basis of interpolation. The calculation of the interpolation is performed based on the distribution of the capacitance changes among those sensors which are claimed to be touched.
The Surface Acoustic Wave (SAW) technology consists of transducers (for transmitting and receiving), reflectors and a controller. The controller sends the signal to the transducer for converting the electrical signals to the ultrasonic waves. The ultrasonic wave is then transmitted to the reflectors for rectifying the waves to the receiving transducers. When a finger touches the screen, some energy of the wave is absorbed so that the touch event can be detected by analyzing the waves received at the transducer.
The infrared touch panel consists of the light-emitting diodes (LEDs), photo sensors and a controller. The controller sends the signals to the light-emitting diodes, so as to drive the light-emitting diodes for emitting infrared beams. The photo sensors are used for detecting the infrared beams. When an object (e.g., a finger or stylus) touches the infrared touch panel, at least a part of the infrared beams are blocked or absorbed. The touch event can be positioned by analyzing the changes of the received signals at the corresponding photo sensors.